Upon starting an overcloud deployment with ceph need to have a check that the Pgnum value can be satisfied.


Environment:

openstack-tripleo-puppet-elements-8.0.0-0.20171228195253.002c4ca.el7ost.noarch
instack-undercloud-8.1.1-0.20171223221738.el7ost.noarch
openstack-tripleo-validations-8.1.1-0.20171221173840.ac39a91.el7ost.noarch
python-tripleoclient-8.1.1-0.20171231084755.el7ost.noarch
openstack-tripleo-ui-7.4.3-4.el7ost.noarch
puppet-tripleo-8.1.1-0.20180102165828.el7ost.noarch
openstack-tripleo-image-elements-8.0.0-0.20180103224254.aad6322.el7ost.noarch
openstack-tripleo-common-containers-8.3.1-0.20180103233643.el7ost.noarch
openstack-tripleo-heat-templates-8.0.0-0.20180103192341.el7ost.noarch
openstack-tripleo-common-8.3.1-0.20180103233643.el7ost.noarch
puppet-ceph-2.4.1-0.20171227224211.fbb6b1c.el7ost.noarch
ceph-ansible-3.0.14-1.el7cp.noarch


Currently it's possible to start a deployment with wrong Pgnum value.
Would be great to have an automatic check that the value can be satisfied by the setup.

Effectively, this can prevent https://bugzilla.redhat.com/show_bug.cgi?id=1539852#c7


Example for manually changing the value - include a yaml with:
parameter_defaults:
    CephPoolDefaultPgNum: 32